Aliaksandr Smirnov

Optoelectronic performance optimization for transparent conductive layers based on randomly arranged silver nanorods.

Optoelectronic performance of transparent conductive layers (TCLs) based on randomly arranged silver (Ag) nanorods (NRs) is simulated. Models for calculation of optical and electronic properties were proposed founded on finite-difference time-domain method and percolation theory respectively. Obtained simulation results are well conformed to experimental data. The influence of angle deviation of NR crossings on the transmittance and sheet resistance are demonstrated. The balance between transmittance and sheet resistance which can be easily set by varying the combinations of NR radius and NR number is shown. Our results demonstrate that randomly arranged Ag layers are promising candidates for flexible TCLs.

Theoretical comparison of optical and electronic properties of uniformly and randomly arranged nano-porous ultra-thin layers

The theoretical comparison of optical and electronic properties of aluminum and silver nano-porous ultra-thin layers in terms of the arrangement and size of the pores was presented. The uniform nano-porous layers exhibit a slightly higher average transmittance (up to 10%) in the wavelength range of the plasmonic response in comparison to the randomly arranged ones. Compared to uniform nano-porous layers, a much larger sheet resistance (up to 12 times) for random nano-porous layers is observed. The uniform and random Ag nano-porous layers possessing the strong plasmonic response over whole visible range can reach an average transmittance of 90 and 80% at the sheet resistance of 10 and 20 Ohm/sq, respectively, which is comparable to widely used ITO electrodes.

Comparative analysis of opto-electronic performance of aluminium and silver nano-porous and nano-wired layers

The comparison of optical and electronic properties between squarely and hexagonally arranged nano-porous layers and uniformly arranged nano-wired layers of aluminium and silver was presented. The nano-wired configuration exhibit 20 and 10% higher average transmittance in visible wavelength range in comparison to square and hexagonal nano-porous designs, respectively. The insignificant difference of the transmittance for aluminium and silver nano-porous and nano-wired layers is observed, when interpore/interwire distance is larger than wavelengths of incoming light. This difference becomes considerable at the interpore/interwire distance less than wavelengths of incoming light: silver nano-porous and nano-wired layers possess up to 27% higher transmittance in comparison to aluminium layers.

Thin porous silicon fabricated by electrochemical etching in novel ammonium fluoride solution for optoelectronic applications

A novel approach to electrochemically fabricate thin nanoporous silicon using ammonia fluoride solution is proposed and experimentally demonstrated. It is shown that highly uniform and thin nanoporous silicon layers (down to 50 nm) with high porosity can be formed in a reproducible manner under low current densities (0.01–0.1 mA/cm2) and low fluorine ion concentration (1%wt). Structural and opto-electrical properties of the porous silicon created in a wide range of current densities and ammonium fluoride concentrations are presented.

Effect of silver nanowire length in a broad range on optical and electrical properties as a transparent conductive film

Optical and electrical properties of silver nanowire transparent conductive films with a broad range of nanowire lengths were studied. A proposed simulation model demonstrated similar behavior with experimental results for 30 and 90 μm nanowires, and thus it was used to expand the range of nanowire lengths from 10 to 200 μm. Theoretical results show that a lengthening of silver nanowires results in an increase of their optoelectronic performance; 200 μm long nanowire possess 13.5 times lower sheet resistance compared to 10 μm ones, while the transmittance remains similar for coverage densities of nanowires up to 25%. Moreover, the dependence of the sheet resistance on the length of nanowires changes non-linearly; from 10 to 20 µm, 20 to 80 µm and 80 to 200 µm the sheet resistance drops by a factor of 5, 2.25 and 1.2 respectively. Furthermore, a thickening of nanowire diameters from 30 to 90 nm decreases the sheet resistance to 5.8 times. Obtained results allow a deeper analysis of the silver nanowire transparent conductive films from the perspective of the length of nanowires for various optoelectronic applications.

Silicon based LED microdisplays: the experience of design and manufacturing

Design and manufacturing process of a full color LED microdislay fabricated by standard CMOS technology and containing an array of aluminum/nanostructured porous silicon reverse biased light emitting Schottky diodes is discussed. Being ofa solid state construction, these microdisplays are cost-effective, thin and light in weight due to very simple device architecture. Its benefits include also super high resolution, wide viewing angles, fast response time and wide operating temperature range. The advantages of full integration of an LED-array and driving circuitry onto a Sichip is also discussed.

Towards understanding the difference of optoelectronic performance between micro- and nanoscale metallic layers

Optoelectronic performance of nano-/microscale porous and wired silver (Ag) and aluminum (Al) layers was theoretically studied. Within the nanoscale region, Ag porous and wired layers – possessing stronger surface plasmon response over the whole visible spectrum –demonstrate up to a 20% higher average transmittance in comparison to identic Al design. In the microscale region, difference in the average transmittance between the above mentioned metallic layers decreases to 5%. Moreover, the microscale Ag and Al layers exhibit up to a 5% higher average transmittance. The obtained results allow deeper analysis of the pattern scale of metallic transparent conductive layers for various optoelectronic applications, such as displays, solar cells, light-emitting diodes, touch screens and smart windows.

P-76: Combined Nanostructured Layers for Display Applications

One-step cost effective process of fabrication of a full inorganic nanostructured transparent conductive electrode and LC alignment layer has been developed. More specifically, the subject comprises a self-organized nanomesh of a valve metal, concomitant porous oxide layer with various functionality and electrochemical method of their fabrication. The nanomesh film is electrically conductive, optically transparent and flexible. It can be fabricated on a variety of substrates, including flexible and rigid substrates. High effective LC alignment layers based of nanostructured alumina can be fabricated at the same anodization process by special electro-chemical technique in sulfuric and oxalic acids to form a self ordered nanoporous structure of alumina which has a “vertical” surface area that prevails over the “horizontal” one even though Al films thickness is small. The possibility to control distances between pores and their sizes during the process of anodizing/etching enables to optimize alignment surface according to the required LC material.

New type of a transparent conductive nanostructured thin film for photonic devices

Electrochemical technologies have high potential for photonic devices because of its cheapness and simplicity, easy to scaling to large substrates and low temperature nature. However, for the most technologies the oxide films should be placed on transparent conductive substrate, usually ITO on glass. For dielectric substrates like glasses a special technology of current control is applied to anodizing metal films, which change the oxide porous structure on final stage and prevent the metal island formation. To transform the residual metal nanowires into oxide special fading process similar to anoding bonding can be done. Usually high reactivity electrolytes are used in anodizing process, which destroy ITO layers. We analyze chemical of ITO in different anodizing electrolytes and find some suitable reagents and compositions. A lot of functional layers can be created by anodizing. For example, different filters may be formed by filling the pores by ink jet printing. Porous oxides can have low refractive indexes — lover than any bulk material, and can be used as effective antireflective cover. Titanium oxide cover film forms “self cleaning” surface due its semiconductor photonics properties and oxygen producing.

Optical haze of randomly arranged silver nanowire transparent conductive films with wide range of nanowire diameters

The effect of the diameter of randomly arranged silver nanowires on the optical haze of silver nanowire transparent conductive films was studied. Proposed simulation model behaved similarly with the experimental results, and was used to theoretically study the optical haze of silver nanowires with diameters in the broad range from 30 nm and above. Our results show that a thickening of silver nanowires from 30 to 100 nm results in the increase of the optical haze up to 8 times, while from 100 to 500 nm the optical haze increases only up to 1.38. Moreover, silver nanowires with diameter of 500 nm possess up to 5% lower optical haze and 5% higher transmittance than 100 nm thick silver nanowires for the same 10-100 Ohm/sq sheet resistance range. Further thickening of AgNWs can match the low haze of 30 nm thick AgNWs, but at higher transmittance. The results obtained from this work allow deeper analysis of the silver nanowire transparent conductive films from the perspective of the diameter of nanowires for va...